Method for optimizing fossil-fueled power stations

ABSTRACT

In a method for optimizing operation of fossil fuel based power plants, in which the economical effects of the changes of selected operational parameters are determined under consideration of the required economical expenditure, and, based on these additional operational costs, it is determined if, when, and/or what kind of measures should be taken for minimizing the additional operational costs. According to the method, the improvement measures are initiated as a function of the cause of the additional operational costs according to a hierarchal catalog of measures. The measures are: an immediate intervention into the operational course; a later measure implemented during a short shutdown; a later measure implemented during a service shutdown; and/or an operational downtime for a revision.

BACKGROUND OF THE INVENTION

The invention concerns a method for optimizing fossil-fueled powerplants (stations).

For fossil fuel based power plants, operating procedures and systems areknown that monitor the power plants during operation and determine theirefficiency. Additionally, methods are known to improve the efficiency ofpower plants during operation by respective control and adjustmentchanges.

To increase and/or maintain the efficiency of power plants above aminimum level, it is necessary to carry out improvement and maintenanceprocedures during which the power plant is shut down. Furthermore, it iscustomary to carry out service, maintenance, and improvement programsaccording to a specified, set time schedule during operation, or duringshutdown of the plant.

The above described customary practice is comparatively inflexible anddoes not take into consideration economical aspects.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide a method for anespecially economically optimized operation of power plants. Theperformance capability of the respective power pant should be used toits full potential by optimizing its operation.

The object of the invention is inventively solved by determining theeconomical benefits of the measures for improving the efficiency of thepower plant and, additionally, the necessary economical expenditures,and by deciding, based on a comparison of the economical expenditures,and by deciding, based on a comparison of the economical benefits andexpenditures of the improvement measures, if, when, and/or whichimprovement measures should be undertaken.

Using the inventive method of comparing the essential economical effectsof improvement measures and the expected economical benefits, on the onehand, with the necessary expenditures for performing the measures, onthe other hand, it is possible to operate power plants in aneconomically optimized manner.

According to an especially advantageous embodiment of the inventivemethod, the improvement measures are modifications to the operatingprocedure and/or interventions during operation, or service,improvement, and/or modification measures during downtime. Duringoperation without downtime, it is advantageous for optimizing theefficiency of the facility to intervene in the process control, forinstance, by blowing soot or correcting excess air etc., whereby,however, the necessary expenditures, for instance, the amount of steamconsumption (or the compressed air consumption) of the utilized sootblowers, is taken into consideration in accordance with the inventivemethod so that an assessment can be made whether the measures to improveefficiency are economically beneficial and, if this is not the case,whether to implement them at a later time or not to implement them atall.

The same holds true for service, improvement, and/or modificationmeasures during downtime. By determining and assessing the expendituresof such measures and/or the economical losses during a shutdown and bycomparing the respective results to the economical benefits of theachieved improvement of the plant efficiency, it is possible to decidenot only in regard to process control aspects, but also in regard to theeconomical aspects, whether improvement measures should be implemented,and, if so, what kind of measures, and, in particular, when suchmeasures should be implemented, for instance, during an alreadynecessary operation shutdown.

According to the inventive method, the current status of the plant,based on measured data, for instance, provided by a process controlsystem, as well as calculations based on plant models, is compared tothe optimized status that can be achieved with operational parameters.According to another embodiment of the invention, to achieve thiseconomically optimized plant status, the improvement measures areevaluated with regard to economical benefits using a catalog ofhierarchical measures. Advantageously, this catalog includes animmediate, hierarchical intervention of the operating procedure, forinstance, for correcting excess air, but also in regard to blowing sootoff selected or all heating surfaces, cleaning the condenser, oradjusting or readjusting injection control circuits. Based on the resultof the cost/benefit analysis, it may be advantageous to take immediateaction during operation or to take advantage of a short shutdown forimprovement measures, for instance, the replacement or attachment of airpreheater sealing material, or to use a service shutdown and/oroperating interruption, performed for a revision, for the improvementmeasures or for more extensive modifications, for instance, for blowerimprovements.

To compare, for example, the benefits of improvement measures with therequired expenditure on an economical basis, the cost savings due to thereduction of excess air must be compared to the higher costs resultingfrom the increase of intermediate superheater injection, and the resultmust be evaluated. For instance, the cost of steam and compressed air inconjunction with the use of soot blowers must be compared to the costsavings resulting from the accordingly lowered exhaust losses.

BRIEF DESCRIPTION OF PREFERRED EMBODIMENT

An embodiment with the following step sequence is very advantageous:

Determination of efficiency loss of the plant by comparing the actualefficiency with the optimal efficiency possible under the actualoperational conditions;

Determination of the costs that will be incurred for improving the plantefficiency by operating process modifications and/or interventionsduring an operational shutdown;

Determination of the economical losses due to the lower efficiency ofthe plant;

Comparison of the costs and the economical losses; and

Decision, based on this comparison, if, when, and/or what kind ofmeasures should be taken.

The actual efficiency (boiler and block) is advantageously determined bymeasured and calculated operational data. Advantageously, the processstatus data are provided by a process control system. It is especiallyadvantageous in this context when the calculation of the operating dataincludes plant model calculations. In this context, the plant models areadvantageously combustion calculations, combustion chamber models,boiler models, models of the steam circulation, whereby these calculatedoperational data are advantageously based on measured operating data,for instance, air and/or flue gas data, electrical data.

These calculated and/or measured operating data provide informationabout, among other things, the degree of contamination of individualheating surfaces inside the boiler, in addition to the determination ofcharacteristic values such as boiler and plant efficiency. Operationoptimization systems that operate according to the inventive method, inparticular, by utilizing computers and computer software, advantageouslyoperate independently of the process control system. The process controlsystem only provides the measured data necessary for evaluationcalculations and processing of operational data.

The determination of the increased operational costs of the actualoperation in comparison to an economically optimized plant operation ispreferably achieved by iterative optimization calculations.

The inventive method is advantageously suitable to save primary energyby recognizing and utilizing the operating reserves of the specificplant. However, the inventive method may also be used with greatadvantage for the following applications:

Assessment of known sources of losses in power plant operations and/orcertain areas of power plant operations;

Indication of plant components that deviate from optimal operating setpoints while taking into consideration operating parameters of theactual load operation;

Maximization of the information contents of measured operating data;and/or

Determination of incorrect or implausible measured data.

The specification incorporates by reference the entire disclosure ofGerman priority documents 196 49 184.3 of Nov. 27, 1996, and 197 48315.1 of Oct. 31, 1997, as well as of International ApplicationPCT/EP97/06466 of Nov. 19, 1997.

The present invention is, of course, in now way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

What is claimed is:
 1. A method for optimizing operation of fossil fuelbased power plants, said method comprising the steps of: a) determiningthe economical effects of the changes of selected operational parametersunder consideration of the required economical expenditure; b)determining, based on these additional operational costs, if, when,and/or what kind of measures should be taken for minimizing theadditional operational costs; and c) initiating the improvement measuresas a function of the cause of the additional operational costs accordingto a hierarchal catalog of measures including: an immediate interventioninto the operational course; a later measure implemented during a shortshutdown; a later measure implemented during a service shutdown; and/oran operational downtime for a revision.
 2. A method according to claim1, wherein the measures are interventions during operation or duringservice, improvement, maintenance, and/or modification measures atoperational downtime.
 3. A method according to claim 1, wherein saidstep a) comprises the steps of: a1) determining an efficiency loss ofthe plant by comparing an actual efficiency value with an optimizedefficiency value; a2) determining the costs resulting from the measuresfor improving the plant efficiency upon changing the operational courseand/or by interventions during the operational downtime; a3) determiningthe economical losses resulting from the efficiency losses of the plant;a4) comparing the costs of the economical losses; and wherein in saidstep b) the cost comparison of said step a4) is used.
 4. A methodaccording to claim 1, wherein in said step a) the actual efficiency isdetermined based on measured operational date and/or calculated data. 5.A method according to claim 4, comprising the step of providing themeasured operational data by a process control system.
 6. A methodaccording to claim 1, wherein in said step a) the calculation of aplurality of the data includes plant model calculations.
 7. A methodaccording to claim 1, wherein the plant models comprise combustionprocesses, combustion chamber models, boiler models, models of the steamcirculation, and/or thermodynamic balance models.
 8. A method accordingto claim 1, wherein a computer program for determining known losssources during plant operation and/or in certain areas of the plantoperation is provided.
 9. A method according to claim 1, wherein acomputer program for determining false or implausible measured data isprovided.
 10. A method according to claim 1, wherein a computer programfor designating plant components that, under consideration of the limitparameters present during actual load operation, deviate from optimizedoperational set point values is provided.